Device and method for growing diamond in a liquid phase

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/044,848 filed on Apr. 14, 2008, which is incorporated herein by reference.

The present invention is directed toward synthesis of diamond in a liquid phase. Therefore, the present invention involves the fields of materials science and diamond synthesis.

Diamond materials have a large variety of applications ranging from gems to industrial application such as semiconductor devices, abrasive tools, and optical devices. Large diamonds can be made by conventional chemical vapor deposition (CVD) methods but these approaches are very slow and costly for more than a few microns in thickness. On the other hand, larger diamond particles have been made by using ultrahigh pressure apparatuses (e.g. belt apparatus, cubic press) with pressures up to several gigapascals under largely solid phase growth of diamond. Due to volume limitations inherent in these devices, the throughput has been low (e.g. one crystal per machine) and the cost has been high. In the case of ultrahigh pressure devices, diamond can grow relatively fast (>1 mm per hour) which is about one order of magnitude higher than CVD diamond.

Conventional CVD diamond film is deposited under partial vacuum at about 900° C. Normally, graphite with sp² hybridization should be the stable phase, but because of the presence of hydrogen atoms (not molecules of H₂), the decomposed carbon atoms from carbonaceous gas (e.g. methane) is bombarded with hydrogen atoms to maintain its diamondoid structure (sp³ hybridization). The growth rate and the quality of CVD diamond are highly dependent on the concentration of hydrogen atoms.

Unfortunately, hydrogen atoms are made by dissociation of hydrogen molecules. This requires a high temperature (>2000° C.), while the mean free path of dissociated hydrogen atoms is short, such that most hydrogen atoms recombine to form molecules to release heat. Consequently, the concentration of hydrogen atoms near the substrate is low. And hence, the growth of diamond film is slow (a few microns per hour). This problem cannot be solved by merely moving the substrate closer to the heat source as graphite will be formed at high temperatures. Thus, conventional CVD diamond processes have a dilemma that high temperature boosts the production of hydrogen atoms, but diamond must be deposited at lower temperature where hydrogen atoms have recombined.

In light of the problems and deficiencies with present diamond synthesis approaches, the present invention seeks to overcome these by growing a diamond mass in a liquid growth medium. The liquid growth medium can include a carbon source, a diamond growth catalyst, and a dissociated hydrogen of a hydrogen source. The carbon source provides carbon atoms for growing diamond. A diamond seed material can also be included in contact with the liquid growth medium for diamond growth such as a plurality of diamond seeds or a crystalline wafer. The molten liquid phase provides a diamond growth catalyst which allows the carbon to form diamond at the temperature and pressure conditions discussed. The diamond growth catalyst can be an alloy of a diamond catalyst metal and a rare earth element, and/or a nanocatalyst as described more fully hereinafter. Furthermore, the dissociated hydrogen acts as a concentrator for assembling carbon atoms at a relatively high concentration which mimicks, in some respects, diamond growth under more conventional high pressure processes without the high pressure.

There has thus been outlined, rather broadly, the more important features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying drawings and claims, or may be learned by the practice of the invention.